Ultramicroporous carbons with extremely narrow pore size distribution via in-situ ionic activation for efficient gas-mixture separation

Developing highly selective, cycle reliable, and moisture resistant adsorbents is of great importance for gas separation. It is very challenging to control and optimize pore sizes within the ultramicroporous ranges (<0.7 nm), especially for biomass-derived carbons. Moreover, porous carbons featured with random micropore sizes usually exhibited inferior gas separation performances. Herein, we developed an in-situ ionic activation method, in which the chemically bonded K⁺ ions that are uniformly distributed in the carbon precursor are able to create ultramicroporous carbons with uniform and narrow pore size distributions. Thus, the obtained carbons exhibited high CO₂ uptakes (4.17 mmol g⁻¹) and selectivities (333.2 and 34.9) for CO₂/N₂ (15v/85v) and CO₂/CH₄ (40v/60v) separation at ambient conditions. The dynamic breakthrough experiments clearly demonstrate their superior and applicable gas-mixture separation performances. Upon the detailed evaluation of vacuum swing adsorption (VSA) working parameters, a record-high adsorbent selective parameter (S) of 1906.4 is obtained. Hence, the in-situ ionic activation approach is an effective method for preparing ultramicroporous carbons with narrow and uniform pore size distributions.